Acmarans are a race of bi-pedaled, humanoid creatures with dark blue skin.
The Acmarans were, according to Averna, once a passionate, freedom loving, yet conflicted race before Taron came into power. With him, he brought talk of obtainable peace and protection through their "true god", an IL-series Cylon called Volahd. After this, many Acmarans began disappearing, only to be experimented upon by the Cylons for the "new life" promised by Volahd. Around this time, the force field, powered by cyranite, is installed to protect the Acmarans, and likely installed to prevent any to escape out to space, as well as to prevent any transmissions from being sent or received (TOS: "The Law of Volahd, Part 2").
However, many Acmarans managed to escape Taron's and the Cylons' forces, fleeing to nearby hills. An Acmaran, Averna, manages to escape undergoing the "new life" process, and is able to deceive Taron and his followers, installing herself in a position to seek out other Acmarans who may have escaped as well.
The Acmarans are later freed from the Cylon tyranny when an angered and betrayed Taron disrupts the energy field, causing the destruction of both the city and Volahd's basestar (TOS: "The Law of Volahd, Part 2").